The invention relates to power transmission belts, and more particularly, to CVT belts comprising a belt trained on drive rings that cooperate with an input and output pulley.
It is well known in the art that a gear type transmission may be used for running a motor vehicle, motorcycle or the like. For the purposes of improving fuel efficiency, a continuously variable transmission, CVT, is preferable. Various types of belts have been developed for use in continuously variable transmissions.
Generally, the CVT Belts have a silhouette similar to that of a conventional V-belt. In particular, they are broad at the top and narrow at the bottom and designed to fit between the sheaves of a pulley that define an angular groove. The pulley on which the belt is trained comprises a moveable sheave and a fixed sheave, both having a truncated cone shape. Generally, one of the sheaves moves while the other remains fixed.
Moving one sheave in relation to the other effectively varies the effective diameter xcfx86 of the pulley within which the belt operates. Consequently, belt speed is a function of the effective diameter of the pulley which is in turn a function of the axial position of the sheaves relative to each other. Generally two pulleys, an input and output, are present in a CVT transmission.
Although each of the prior art CVT belts are flexible, each also has characteristics not found in other power transmission belts. For example, the belts are required to have transverse rigidity. This allows the belt to run at a particular effective diameter without being crushed between the pulley sheaves. Consequently, each CVT belt system comprises a belt trained around variable diameter pulleys.
Regarding the prior art relationship between the pulley and the belt, U.S. Pat. No. 5,709,624 to Donowski discloses a variable diameter pulley. A single drive ring runs in the sheaves of the pulley. A flexible belt runs on the drive ring through the pulley. As the sheaves move with respect to each other, the effective diameter of the pulley is changed. Since the drive ring bears the transverse or compressive forces between the sheaves, the belt need not be designed to accommodate these forces. However, the Donowski device comprises a single drive ring used as a part of an auxiliary drive system of an internal combustion engine. A stabilizing member is also required to maintain the axis of rotation of the drive ring as least substantially parallel to the axis of rotation of the sheave members. The Donowski device does not lend itself to use in a CVT transmission.
Also representative of the prior art is U.S. Pat. No. 6,017,285 to Yasuhara, which discloses a variable diameter pulley with a power transmission ring held between the power transmission surfaces of the pulley. A belt is engaged with the outer circumference of the power transmission ring. The pulley bodies are biased toward each other with a biasing means, a belleville spring. The belleville spring couples the pulley bodies to each other for power transmission. This device requires a biasing means to realize power transmission from the pulley to the drive ring.
Also representative of the prior art is U.S. Pat. No. 4,875,894 to Clark, which discloses a continuously variable transmission. The transmission comprises an input and output shaft, each having a rotary disk assembly. The rotary disk assemblies each have contact pads which form circles having continuously variable diameters. The two rotary disk assemblies are connected by a coupling mechanism, such as a rigid coupling ring. Power transmission occurs between each pulley through rotation of the ring. This device does not offer the option of using flexible belts for power transmission, requiring instead the rigid ring to connect the two disks. This limits the space that the device can operate within, generally to a square or circular space defined by the extreme outer dimension of the pulleys.
What is needed is a drive ring CVT belt having cooperating drive rings. What is needed is a drive ring CVT belt having a flexible member trained around the pulley drive rings. What is needed is a drive ring CVT belt having drive ring alignment sleeves. The present invention meets these needs.
The primary aspect of the invention is to provide a drive ring CVT belt having cooperating drive rings.
Another aspect of the invention is to provide a drive ring CVT belt having a flexible member trained around the drive rings.
Another aspect of the invention is to provide a drive ring CVT belt having a constant belt loading radius.
Another aspect of the invention is to provide a drive ring CVT belt having drive ring alignment sleeves.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a drive ring CVT belt. In a CVT transmission, each variable diameter pulley has a drive ring trained around the sheaves. Each drive ring may comprise any high modulus material such as plastic or metal. An endless flexible tensile member or belt is trained between the drive rings. Each drive ring further comprises a sleeve that is trained around an alternate outer surface of each drive ring. Each sleeve then slides in a bushing on its respective drive ring. The belt has a tensile load that presses each of the drive rings together on the sleeves. The relative arrangement of the axis of rotation of each drive ring is maintained by the contact between the sleeves and the drive rings. The effective diameter or radius of each pulley is adjusted by movement of the pulley sheaves. Movement of the pulley sheaves causes the axis of rotation of each drive ring to move eccentrically with respect to the axis of rotation of the pulley. As the rings move, the belt moves with the drive rings and remains trained over the drive rings, giving a constant bending radius to the belt. The drive rings each may have a surface profile for use with synchronous belts, toothed belts, multi-ribbed belts or v type belts.